<!--
 * @Description: 
 * @Author: charles
 * @Date: 2021-08-10 15:17:25
 * @LastEditors: charles
 * @LastEditTime: 2021-08-10 15:20:51
-->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>伪元素</title>
  <style>
    ul {
      list-style: none;
    }
    ul.menu {
      background-color: tomato;
    }
    ul.menu > li{
      float: left;
    }
    ul.menu::after {
      content: "11";
      display: block;
      clear: both;
    }
  </style>
</head>
<body>
  <ul class="menu">
    <li>one</li>
    <li>two</li>
  </ul>
</body>
</html>